The battle of Arni (3 December 1751) was a second victory won by Robert Clive late in 1751, and helped secure his conquest of Arcot. In the summer of 1751 the British were in a weak position in southern India. The French, under Joseph Dupleix, had helped their allies gain the key positions of Nizam of Hyderabad and Nawab of the Carnatic, while the British-supported candidate for the second post was besieged in Trichinopoly.
The situation was partly restored by Robert Clive. He captured Arcot, the capital of Chanda Sahib, Nawab of the Carnatic, and then held it against a counterattack (siege of Arcot, September-November 1751).
The siege had been conducted by Chanda Sahib's son Raju Sahib. After the failure of his assault on the city, Raju Sahib retreated towards the fortress of Vellore. Although more than half of his army deserted him, Raju Sahib still had 4,500 of his own men (2,500 infantry and 2,000 cavalry) and reinforcements from Pondicherry brought his French contingent up to 300.
Clive had been reinforced since the end of the siege, and he now had 200 European troops, 700 Sepoys and 600 Maratha cavalry. When he discovered that Raju Sahib had left Vellore to join up with the French reinforcements, Clive decided to try and intercept him before he could return to Vellore. After a forced march Clive caught up with Raju Sahib at the Arni River, south of Arcot and south-east of Vellore. Raju Sahib decided to take advantage of his superior numbers, and attacked Clive.
The battle was fought in an area of paddy fields, crossed by a single causeway near a village on Clive's right. Clive posted his Sepoys in this village, his Maratha cavalry on the left and his British troops in the centre.
Raju Sahib attacked at around noon. His artillery could only move on the causeway, and this exposed it to fire from the Sepoys in the village. This first attack stalled. The French troops then attempted to advance using a traveller's shelter as cover, but they were attacked in the flank by the Sepoys and were broken.
After this setback Raju Sahib's army retreated. The Maratha cavalry pursued his cavalry force, while Clive followed the infantry with his own infantry and field guns. Raju Sahib's army scattered across the countryside, and didn't regroup until it reached the fortress of Gingee. The French suffered fifty casualties during this battle, while Raju Sahib's Indian forces lost 150 killed and wounded. In contrast Clive lost 8 sepoys and 50 Marathas. He also gained 700 French trained Sepoys who enrolled with the British.
This was Robert Clive's first battlefield victory, and helped to secure British control of Arcot. After the battle Clive captured Congeveram (16-18 December 1751), put a garrison into Arcot and then returned to Fort St. David.